de.schlichtherle.truezip.zip.LittleEndian Maven / Gradle / Ivy
/*
* Copyright (C) 2005-2015 Schlichtherle IT Services.
* All rights reserved. Use is subject to license terms.
*/
package de.schlichtherle.truezip.zip;
import javax.annotation.concurrent.ThreadSafe;
/**
* Provides static utility methods for reading and writing integer values in
* little endian format from or to byte arrays.
*
* @author Christian Schlichtherle
*/
@ThreadSafe
final class LittleEndian {
/** This class cannot get instantiated. */
private LittleEndian() {
}
/**
* Reads a signed byte integer value from the byte array
* {@code buf} at the offset {@code off}.
*
* @param buf The byte array to read the signed byte integer value from.
* @param off The zero based offset in the byte array where the signed
* byte integer value is read from.
* @return The signed byte integer value read from the byte array.
*/
static byte readByte(final byte[] buf, final int off) {
return buf[off];
}
/**
* Reads an unsigned byte integer value from the byte array
* {@code buf} at the offset {@code off}.
* Note that it is not necessary to check the return value with
* {@link UByte#check}.
*
* @param buf The byte array to read the unsigned byte integer value from.
* @param off The zero based offset in the byte array where the unsigned
* byte integer value is read from.
* @return The unsigned byte integer value read from the byte array.
* Java does not provide {@code unsigned short} as a primitive
* type, hence an {@code int} is returned which's three most
* significant bytes are zero.
*/
static int readUByte(final byte[] buf, final int off) {
return buf[off] & UByte.MAX_VALUE;
}
/**
* Reads a signed short integer value from the byte array
* {@code buf} at the offset {@code off}
* as two bytes, low byte first.
*
* @param buf The byte array to read the signed short integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the signed short integer value is read from.
* @return The signed short integer value read from the byte array.
*/
static int readShort(final byte[] buf, final int off) {
return (buf[off + 1] << 8) | (buf[off] & UByte.MAX_VALUE);
}
/**
* Reads an unsigned short integer value from the byte array
* {@code buf} at the offset {@code off}
* as two bytes, low byte first.
* Note that it is not necessary to check the return value with
* {@link UShort#check}.
*
* @param buf The byte array to read the unsigned short integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the unsigned short integer value is read from.
* @return The unsigned short integer value read from the byte array.
* Java does not provide {@code unsigned short} as a primitive
* type, hence an {@code int} is returned which's two most
* significant bytes are zero.
*/
static int readUShort(final byte[] buf, final int off) {
return ((buf[off + 1] & UByte.MAX_VALUE) << 8) | (buf[off] & UByte.MAX_VALUE);
}
/**
* Reads a signed integer value from the byte array
* {@code buf} at the offset {@code off}
* as four bytes, low byte first.
*
* @param buf The byte array to read the signed integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the signed integer value is read from.
* @return The signed integer value read from the byte array.
*/
static int readInt(final byte[] buf, int off) {
off += 3;
int i = buf[off--]; // expands sign
i <<= 8;
i |= buf[off--] & UByte.MAX_VALUE;
i <<= 8;
i |= buf[off--] & UByte.MAX_VALUE;
i <<= 8;
i |= buf[off] & UByte.MAX_VALUE;
return i;
}
/**
* Reads an unsigned integer value from the byte array
* {@code buf} at the offset {@code off}
* as four bytes, low byte first.
* Note that it is not necessary to check the return value with
* {@link UInt#check}.
*
* @param buf The byte array to read the unsigned integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the unsigned integer value is read from.
* @return The unsigned integer value read from the byte array.
* Java does not provide {@code unsigned int} as a primitive
* type, hence a {@code long} is returned which's four most
* significant bytes are zero.
*/
static long readUInt(final byte[] buf, int off) {
return readInt(buf, off) & UInt.MAX_VALUE;
}
/**
* Reads a (signed) long integer value from the byte array
* {@code buf} at the offset {@code off}
* as eight bytes, low byte first.
*
* @param buf The byte array to read the signed long integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the (signed) long integer value is read from.
* @return The (signed) long integer value read from the byte array.
*/
static long readLong(final byte[] buf, int off) {
off += 7;
long l = buf[off--]; // expands sign
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off] & UByte.MAX_VALUE;
return l;
}
/**
* Writes the integer value {@code b} to the byte array
* {@code buf} at the zero based offset {@code off}
* as one byte.
* The most significant three bytes of the integer value are ignored.
*
* @param b The integer value to be written.
* @param buf The byte array to write the integer value to.
* @param off The zero based offset in the byte array where the byte
* of the integer value is written to.
*/
static void writeByte(int b, byte[] buf, int off) {
buf[off] = (byte) b;
}
/**
* Writes the integer value {@code s} to the byte array
* {@code buf} at the zero based offset {@code off}
* as two bytes, low byte first.
* The most significant two bytes of the integer value are ignored.
*
* @param s The integer value to be written.
* @param buf The byte array to write the integer value to.
* @param off The zero based offset in the byte array where the first byte
* of the integer value is written to.
*/
static void writeShort(int s, final byte[] buf, final int off) {
buf[off] = (byte) s;
s >>= 8;
buf[off + 1] = (byte) s;
}
/**
* Writes the integer value {@code i} to the byte array
* {@code buf} at the zero based offset {@code off}
* as four bytes, low byte first.
*
* @param i The integer value to be written.
* @param buf The byte array to write the integer value to.
* @param off The zero based offset in the byte array where the first byte
* of the integer value is written to.
*/
static void writeInt(int i, final byte[] buf, final int off) {
buf[off] = (byte) i;
i >>= 8;
buf[off + 1] = (byte) i;
i >>= 8;
buf[off + 2] = (byte) i;
i >>= 8;
buf[off + 3] = (byte) i;
}
/**
* Writes the long integer value {@code l} to the byte array
* {@code buf} at the zero based offset {@code off}
* as eight bytes, low byte first.
*
* @param l The long integer value to be written.
* @param buf The byte array to write the long integer value to.
* @param off The zero based offset in the byte array where the first byte
* of the long integer value is written to.
*/
static void writeLong(long l, final byte[] buf, final int off) {
buf[off] = (byte) l;
l >>= 8;
buf[off + 1] = (byte) l;
l >>= 8;
buf[off + 2] = (byte) l;
l >>= 8;
buf[off + 3] = (byte) l;
l >>= 8;
buf[off + 4] = (byte) l;
l >>= 8;
buf[off + 5] = (byte) l;
l >>= 8;
buf[off + 6] = (byte) l;
l >>= 8;
buf[off + 7] = (byte) l;
}
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